For Reading:

"I Know That" Language Skills
Play "Punctuation Paintball"
Play the "Word Carnival"
Play Word Games at I-love-dogs.com
Learn about the "main idea" of a paragraph at studyzone.org

  For Math:

"Count On" Math Games
Learn to Add, Subtract, Multiply & Divide with Leon's Math DOJO"
A Game for Learning Your Multiplication Tables
A Website That Will "Create A Graph"

  For Science:

"I Know That" Science Skills